C++ notes 6.1

1. Only the decimal system has negative numbers, and the octal system starts with 0.
2. The fprintf function can only be written to the file in the form of a string; the
fputc function is written to the file in the form of characters; the
fwrite function can store the integer number in the file in binary form.
3. In a 64-bit system, sizeof(char*)=8, sizeof(char)=1.
4. Operators that cannot be overloaded in C++ are?: ::. .*
5. When defining a two-dimensional array, the row can be defaulted, but the column cannot, and must be initialized.
6. Every function can have return, including void type, return can appear multiple times in the same function.
7. In order to avoid plastic overflow during the operation, you can ① detect the change of the sign bit ② subtract the addend from the calculation result to see if it is equal to another addend